IG with 2 skimmers and bottom return line.

I'm concerned about one of my skimmer lines. When I leave only one of the lines open...either bottom or near my pressure drops maybe 1 or 2 points. When I turn only the far skimmer on My pressure drops by half. Also, the near skimmer has an easily visible "current" inside and easily pulls my skimmer sock down when I put the basket in.

When all valves are open the far skimmer has been lightly floating and there is no visible current inside the skimmer. If I put my hand in the bottom almost completely covering the hose hole I can feel a good draw. But this seems pretty weak.

When I opened the pool I used a shop vac to clear the "anti-freeze" from the lines. from one of them I pulled a large nut or a small pit. Later I checked my pump basket and there was a decent sized stone.

It seems to me I have a blockage but I don't know what to expect. More importantly I need suggestions on how to fix if there is a problem.

Ideas or suggestions?